I am really into both Scottish and Japanese history and I have noticed quite a lot of similarities, they both had warlords, clans, warriors etc. And I was wondering if it may have something to do with the landscape. Scotland and Japan both have similar landscape with a distinct highlands and lowlands and both have some of the oldest mountains and volcanos on earth. The appearance of the landscape and the history of Scotland and Japan is extremely uncanny and I would go as far to say that Scotland is a mini Japan just at the other side of the world (just not and island). So why are these two countries from two corners of the world so similar even though at the time the people would’ve never met each other before?
Any two human societies when compared can have similarities. Warlords, clans, and warriors are not distinct to Japan or Scotland. Throughout history and throughout the world's continents there have existed individuals of exceptional military power, family groups unified under specific interests, and martial peoples who serve to defend and protect the interests of their realm. It's a matter of human phenomena and the nature of how we respond to the world and situations. Limited resources and competing powers means conflict over said resources, thus, if we examine the rough landscapes of Japan and Scotland, naturally we can expect the inhabitants of such lands to follow such a trend. From there I'm afraid I fail to really see why Scotland and Japan specifically have drawn your interest so much, you'll have to provide more examples of similarities for further explanation. Once again, warlords, clans, and warriors are not unique to the Scottish in Europe or the Japanese in Asia. The only concrete parallels I can think of when connecting the two societies is the establishment of numerous whiskey distilleries in Japan during the twentieth century, for example the successful Yoichi facility was built in Hokkaido due to the supposed similarities in climate to the Scottish highlands. Even still, that is unrelated to your question. Japan's political structure, religious beliefs, interactions with its neighbors, etc, is quite unlike Scotland, but I can think about any number of similarities and differences given enough time.
In times and areas without a strong central government and a large bureaucracy, it is extremely common for societies to construct political groupings (and thereby a method of military mobilization) based on kinship ties real or imagined. This is not in any way exclusive to Japan or Scotland. At a risk of delving into pop-science, you might even say this was a logical outcome of human evolution as a social animal.
Beyond that, much of the similarities are superficial only. In fact, the word "clan" is just a very impercise translation convention used to denote one of very many related but different things in Japanese history. /u/Morricane and I went through the different things that were translated into English as "clan" here.